Laurent Demaret has written a good article about how he systematically troubleshooted cache buffers chains latch contention, starting from wait interface and drilling down into details with my latchprofx tool:

For my new book on Oracle indexing, I’d like to provide guidance on detecting when the block references in a secondary index on an index-organized table (IOT) need to be updated. All that I could find using my second brain were unsubstantiated claims that a secondary index should be rebuilt when PCT_DIRECT_ACCESS falls below 30. [...]

DBAs with a few years of experience and/or having read some material on performance tuning know that eliminating physical reads and achieving a high buffer cache hit ratio isn't necessarily a tuning goal.Some DBAs have accepted the idea that, rather than physical reads, they should concentrate on logical reads -- consistent gets in case of queries.But ...... there really is no "absolutely correct optimization target". Everything is relative.

PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. PHP is the popular programming language to produce dynamic web pages. You can see many applications/frameworks what were developed by PHP programming language.